Mud, Muscles and vitamin D

The days are closing in as autumn and winter approach. For many athletes, this means moving workouts and training sessions indoors. Even when training outside during the colder months, the low sun, cloud cover, and wearing clothes prevent our bodies from converting sunlight to vitamin D.


Fran was unlikely to get his vitamin D dose from the sunshine today

At the London Irish training ground in Sunbury, rain or shine, rugby and fitness training takes place out on the pitches. Muddy, wet, and cold may not be pleasant, but it prepares everyone for real game day conditions. I’m all for a bit of mess, until I get a muddy mountain of washing dumped in the laundry basket at the end of the day. In winter it’s not just shorts, T-shirts and socks, but tracksuit bottoms, tops, Skins and jackets. Would it be unreasonable for me to politely suggest a laundry room at the new training ground at Hazelwood?! So to my point…..when covered with clothes (and mud!) any small amount of vitamin D provided by the sun in winter, won’t reach the skin.

For those training near the equator, sunlight and vitaminD aren't such a problem

For those training near the equator, sunlight and vitamin D aren’t such a problem

The importance of sunlight and sports performance has been known for centuries, but it is only recently that the science behind the physical benefits have been investigated. We are still in the early days of discovering the tiny details of how vitamin D affects muscles. Other benefits of vitamin D have already been established e.g. for the prevention of diabetes, heart disease and some cancers.

Scientific studies are slowly piecing together how vitamin D affects muscle. This is what we know so far about vitamin D and involvement with muscle:

  • muscle contraction – calcium and phosphate are essential for the muscle fibres to move, and vitamin D may help this mechanism to work. Vitamin D may also be important for the actual parts of the muscle that make the contraction work (actin and myosin)
  • muscle repair – after exercise, there will be damage to the tiny muscle fibres. Vitamin D may help to repair this damage
  • muscle building – vitamin D stimulates new muscle, and the blood vessels feeding the muscles

In real life?

Although studied at a cellular level, there aren’t many studies yet on vitamin D and how levels in young, healthy athletes affects performance. However, in elderly people, low vitamin D has been shown to result in poorer muscle function and muscle loss.

Should I supplement?


Vitamin D spray

There are very few good food sources of vitamin D, it comes mostly from the sun. Some foods, like breakfast cereals have vitamin D added, and if you take a multivitamin it may contain some vitamin D.

I advise to take a daily supplement of vitamin D during the winter months (October – May). Unless otherwise advised by your doctor, up to 1000IU per day is safe for adults. It comes in tablet, drops or spray form.

If you aren’t sure how much vitamin D you are getting, I can perform a nutritional analysis of your current diet and the supplements you are taking, and advise you on improving your diet. You can get in touch using the contact form.

Information from Nutri-facts


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